Research Of DB2 Database Query Optimization For Management Information Systems

Information system associates with data management, and associates with database. Information system integrate with database, has become the bottleneck of information systems by now. Therefore, apply the theory of database optimization to information system, will greatly improves accessing database, and promotes the rapid development of information systems.Over the years, the productions of commercial databases have been improving the performance of queries. There are five steps in DB2 query processing: parsing, semantic processing, query transformation, query optimization, and code generation. The optimizer generates many equivalent execution plans for satisfying the query, and then estimate the execution cost, the optimizer chooses the fastest plan based on the estimated costs. When optimizer choosing the best access path, it calculates the filter factor based on statistics, and then calculates the CPU cost and I/O cost, so get a total cost. Statistics plays a grate role for optimizer. Proper index can help DBMS fetch the data quickly; reduce the cost of I/O, so the proper index also play a great role for optimizer. In the development of information system, we must follow the followings: create proper database, write correct and proper SQLs, collect statistics the more the better, created proper indexes. In addition, reduce the times of information system accessing the database.Apply query optimization to information system, will helps DB2 choosing the proper access path, improves information systems performance, and contributes to information systems further development.